I saw your post. Please note that I am not in any way criticizing you. Just stating reasons why some of the board people might be posting such replies, using their reasoning.
I think what incited people there to give you a hard time is because your first post was a FS thread for a poster that is currently being sold for under $150 shipped on average at this point in time; plus, being that it's your first post, you have yet to contribute anything to the boards -- this includes post count, database updates, financial contributions, etc. In addition to that, when it comes to making sales and trades, these things are all looked at because unlike ebay, there is no one to police these things on eb -- except paypal claims, but even that is not all protecting. Not many want to trade nor buy with a new member who has not contributed anything because he/she could be a scammer and who knows if they even know how to properly pack and ship a poster? It's somewhat like buying off ebay and going off a person's feedback. With EB one is more likely to buy from someone they see around the forums more often that has established themselves with a sort of reputation.
Additionally, the poster has been stored in a tube as opposed to flat. People who have been in the poster game for a while do not want a poster that has been stored in a tube. As soon as you get your poster, it should be flattened and stored correctly or framed. Never leave it in a tube. The kraft paper is not acid-free for one; additionally, it will make it a lot harder or maybe even impossible to ever make it perfectly flat again after that. The value of it is thus lower than those that have been stored flat.
As for the next Ghibli, it's Porco Rosso but no new info yet.